Nice, given how the discussions were going some months ago I was worried that they would pick some closed source solution like Discord or Slack. I have not used Matrix so I do not know how good it is, but I do not like the lock-in of Discord and Slack.
Agreed, this is a huge relief. I was getting quite worried that Mozilla would go to Discord, like Rust and other projects have done. I don't know anything about Matrix, but I know it's free, and if it has Mozilla's endorsement, now I'm actually curious to try it... maybe even via an IRC bridge!
FYI #rust-beginners is on discord, but many of the teams have transitioned to Zulip because it has threads. I'd love if Zulip was OSS, but at least it's a highly innovative company that's improved a lot on the UX of IRC (far beyond not needing to setup a bouncer).
The mismatch between Discord's targeted audience of gamers can get funny at times. One rust dev has had their status we to "playing systemd" for days.
Edit: How did I miss that Zulip is open source??? Thank you to the commentators who pointed this out, you made my day :)
Edit2: Just learned what I said about rust decision-making was totally wrong. Thanks to Rob Pike in the other thread for his detailed comments.